Heat exchange apparatus



Dec. 5, 1944.

G. E. CLANCY HEAT EXCHANGE VAPlsvaRmUs Filed March 2, 1942 lexhaustpipe. ,l

, The` general object of,` the (present Ainvention is Patented Dec.`5,`1944 N -UNITlEDY- STATE S PATENT om@ iHiiATxCHANGEArPARArri-isi" y lGilbert E;` ClaneylLos Angeles, Calif., assignor to ffnfApplieationMarsh 2, ieiaserialln.'iaalesaff` iolaiin.; (Cim-241i This inventionrelates generallyytotheat exichangeapparatus,zand` more. particularlyto; uid heaters and boilers Aidesignedx to utilizethe waste 'heat ":ofexhaust gases lofi. anfaircraft or 'f other internalN combustion engine,though sarly :limited thereto. f l l being 1in aceordance (withthefbroken line l--gl of Aircraft :of modernwdesignlare commonly i4equippedwith,cabin heating systems and `with water heaters, and" may"havefiuse `for steam as` a medium 'for' driving l `the turbines f ofngenerators andtthelikei Heat exe-hangers designed to derivetheffheatforjsuoh typical f needs from the exhaustl 'gases of!! theengine have fbeen `incorporateddireotlyin the exhaust pipe. `The exhaustpipe of alarge aircraft may be, for `instance, abo-util"` in diameter,and the exhaust gases owing through thpipewillirange in tem'- peraturebetweenY 1200`jarid` 17009 "Under such conditions,` the heat exchangermay, if `properly designed, derive sullicientheat for all these needs`from the exhaust gases,`th0ugh prior leflortsu to "providelsuitableapparatus of the gclassinentioned fthe provision ofa heatfexchange,arrangement yieldingl a sufeientl'y high rate of heat" transfer"between "the exhaust `gases and the ,.flld'tobe "heated and finally;the provision lof.; a. construction "which, does notV set [upobjectionable turflo Fig. 3 `isa fragmentaryview showing agportron orvthe l metal plank tof f Vwhich the shell for the .boiler is` formedprior to;V `formation ofthe radial indentationsrand i l `Eig; 4` is adetailV similar to a` portion of Fig. ,2,` but showing a modification. v

" l` The briller` of the'lpreserit'invention; designated generally bynumeral I0;;emb'odies a tubular shell as the exhaust pipeioan aircraftengine. Thus, i

or' sleeve fl l formed tyiiiicallyand` preferably of lligaugesheet'steelnadapted to be made` upzas a section` orlasnconduit; carryinghot gases, such as here typically illustrated, thesleeve. I'I isshown as`receivingWithints right:` lfiandfend,- the end lportionof`exh'alistfppe section` IZ, understood: to lead from theexhaustmmanifoldrof van aircraft` engine;` and as .received at its `lefthand end within the end portionief"ei'zliaustpipe section: i 27 under-Stood to dischargeto atmosphere. n Sleeve Ill is i secured tothe exhaustpipe section" |2xeand lf2` in any 'suitable manner, las for nstanceixbymeans V'of screws `I4 passing through perforated lugs iso l of `thesleeve With-allfitemperaturechangs to` "lISand/Wisee" lg; l); i

"Illle'sleeve" Il is formed with a plurality of `lorigitu'dinal'lyextending lexpansionfjoints, permitting `ne cessa-ry `radial `expansionl and contraction 'Which the boiler', issubjected `3In the: presentbulence inthe exhaustgases, nor inrany other way materially increasethe` back `pressure in` the ,to provide a simple, ,ruggedgand relativelyinexpensivegfwaste heat)heater4 for ,boiler `which overcomes Vallfofithe .abovelmentioned prob1ems. l 1- .With thislgenerallobjeotiinlview,I`now proceed Atoa detailed `descir'ilntion of onepresentpreferredillustrative yeiiibodirrlent :of the invention,

.reference Abeing had to "theaccompanying draw:-

l is an` elevation, :With-.parts brokenzaway,

`of `a boiler in accordance iwiththe presentinvention indicatedTaal:made up iirraniexhagust 1 pipe `such lasthatvoian-aireraftenginepthenbroken r laway portion at thefright-nand end erthe view 1555 nreferredfembodiment'of the invention,` theseexparisienjoints? are inf the 1form of a plurality oi annularly spaoedlongitudinallyextending in- -dentatins v2 n; bent'inwardly substantiallyradially ifr'o'ii'i the-metal of the' sleeve, and extendingsubfstantiallyfrom vend to end :ofA the sleeve `in `direoi tions`parallel to its; central longitudinaltaxis.` i fis `best shown inY Fig;2yeach such indentation is deiined .by @two longitudinally `extendingwall por- `tionsfl `forming ,a'reentrant -angleof for instanceabuttwoprlthreedegrees (the drawing showsfthe anglefsomewhat exaggerated),affordingtfsubstantial freedomefor radial and eircumferentialcontraction or; expansion. The inden- Vtations 20 may extendinwardlywithin' the sleeve typicallyuand preferablyv to adistanee substan- .1.'50

tiallyhalf itsfradius; l `Indelfitations, `20,.iyterminate. `Just shortof the connections"oi-tl'xegsleeveV Il with the exhaust .pipe; as`indicatedfat .20a (Fig.` l), and `the end fiplortions of thesleeve,joutwardly of the ends of Ithe indentations," are closedto-permit the effecting of a proper closure with the exhaust pipe. Themanner of accomplishing this closure will be apparent from aconsideration of Fig. 3, which is la detail showing a fragmentary endportion of the initially flat rectangular blank from which the sleevewill be understood to be formed. In Fig. 3, B designates the fragmentaryportion of the blank,and letter C an edgewhich is eventually to becomeone end of the sleeve. Edge C is-forrned with a plurality of rectangularnotches such'as abcd, one for each of the indentations (but one suchnotch appearing in Fig. 3), and it will of course be understood that theedge of the blank opposite to edge C will be formed with correspondingnotches of the same kind'. The

.metal is severed for a short distance beyond points b and c, to form astraight edge ebcf. The

yits flat sides in contact with the sleeve, substanmetal is then bentinwardly along longitudinal gifcrease lines eg and fh, being at the sametimer folded in the reverse direction at crease line i9' to form theapex of the indentation. 'I'hus the areas represented by egyi and fhaiwill forni the two walls 2| of the indentation. In this operation, edgesab and cd are butted against one another, and they are then weldedtogether, as indicated at 24 in Fig. l. The openings then left at theends of the wall members 2| (between the edges represented by ei and fiin Fig. 3)V are closed by welding, as indicated at 25 in Figs. l and 2.

In the particular embodiment of the invention here disclosed, the sleeveor shell is, as stated, formed from a rectangular blank, so that alongitudinal seam is necessarily provided. This. may

conveniently be located at the apex of ,one of the indentations 20, andthe seam closed by welding, as indicated at 26 in Fig. 2.

Mounted on the sleeve is a. coil 30 compris.. ing a number of spacedturns of steel tubing 3|, preferably and here shown asilattenedsomewhat, so as to increase the area of contact with thesleeve. This tubing is welded along each of its edges to the sleeve asindicated at 21, so as to reduce materially the resistance to flow ofheat from the sleeve to the tubing. However, as will be evident from thedrawing, the weld-integration of the tubing to the sleeve isdiscontinuous, being interrupted Wherever the tubing bridges across anAindentation 20.

The end of the coil,at the downstream end of the sleeve |b| is connectedto the supply of water or other liquidV to beheated or evaporated,

, and the other end of the coil is of course connected to whatever istobe supplied with the hot water, steam, etc.

The hydraulic radius of the sleeve is reduced, and the pick-up of heatfrom the exhaust gases correspondingly augmented, by the use of radiallydisposed longitudinally extending fins here illustratively shown aswelded to the interior surface of the sleeve. These fins 35 arepositioned in parallelism with the central longitudinal axis of thesleeve, so as to avoid setting up turbulence in the exhaust gasesflowing through the sleeve, as wellasvthe creation of back pressure on.the engine, and they are preferably and herev shown as extending abouttwo thirds of the distance from the wall of the sleeve to its center,the fins being here sh-own as uniformly spaced between the radial heatexpansion indentations 20.

The boiler as thus described has many unique advantages. Consideredfirst from the standpoint of heat transfer, the following features areto be noted. The radial fins 35, as well as the radial indentations 20,reach deeply into the eX- tially -increases the area. of contact betweenthe sleeve and the coil, and hence further materially increases the rateof heat transfer. Moreover, the attening of the tubing reducesitshydraulic radius,v and hence increases the rate of heat transfer fromthe tubing to the water or other liquid contained therein, as will beevident to those skilled in the art.

The indentations 20 and the fins 35 both function as heat interceptingand conducting fins, be-

-ing designed to absorb a substantial quantity of heat from the gasesand to `convey heat at a rapid rate to the sleeve gig. 4 shows amodiiication, in which the fins 35a are tapered in thickness, beingthickest at their butt ends, that is, at point of juncture with thesleeve. Since all portions of the fins absorb heat from the hot gas, andsince the heat intercepted by the-fins ows outwardly toward the sleeve,the quantity of heat carried` by the fins necessarily increases in thesame direction, with some tendency to overheat theouter portions of thefins. The described thickening of the fins toward their butt endsaccommodates this increased heat flow'.

The coil of the boiler as described cannot burn out even though operateddry. This follows from the fact that the heat radiation surface of thecoil, arranged on the outside of the shell, is equal to or greater thanthe radiation surface of the sleeve, and so long as the sleeve itselfdoes not burn out, it is impossible to convey sufcient heat from thesleeve to the coil to burn out the latter.

Neither the sleeve nor the coil is subject to fracture under the rathersubstantial expansive forces arising either from the extreme heat towhich the apparatus is subjected, or from pos' sible freezing of waterin the coil. The described expansive joints in the sleeve allow it toexpand or to contract radially and circumferentially, or to twistsomewhat about its 1ongitudinal axis to accommodate itself to anystresses placed upon it under any contemplated service conditions. asWeld-integrated to the sleeve, but with a necessary break in the weldline whenever the tubing bridges across an expansion joint. This resultsin a structure having, some capability for yielding torsionally aboutits central longitudinal axis with any torsional stress that may be setup owing to differential rates of expansion or contraction between thesleeve and the coil. The structure as described is capable of expanding,contracting, or working or giving in any required direction, with anystress placed upon it owing to high heat, rapid temperature changes, orfreezing up, all possibility of fracture resulting from any temperatureconditions which will be experienced under service conditions havingbeen eliminated.

The flattening of the tubing of which the coil Vis composed safeguardsagainst bursting of the coil upon freezing up. Thus, since the cross-The described weld-integration TheV coil has been described i pressureon the engine. i Certain of the advantageous features of strucv ductingsurface. i

sectional area of `a round tube is greater `than `that of a flattenedtube, if water left in the `coil should freeze, and therefore expand,Vthe eiect i will be merely to force the attened tubing to assume a morerounded shape, such change of shape being sufficient to provide theincreased volume required.

The disposition of the indentations 2|!` and fins 35 in planes parallelto the sleeve is of im,-

possibility of fracture of the structure under any temperature conditionwhich may be experienced in practical service, impossibility of burningout the coil, even if dry, and substantially complete avoidanceofincreasing theback ture and operation which have been described 2o Icircumferentially spaced and longitudinally exi tending openindentationswhich project inward-` apply` to heat exchangers in general as Well asto boilers, and apply also Whether the high temperature fluid or the loWtemperature fluid `oWs through the inner sleeve. For instance, the

provision of the expansion and contraction joints 20 takes care of thestresses which would i otherwise `be set up by differential expansionsor metallically bonded with the first member, car-` ries a uid atanother temperature. In any such circumstances the expansion joints 20ac- 3()` contractions in such a structure Where one 1 member (theinnerimember here) carries fluid at one temperature, and the othermember (the outer `member here) in metallic contact orV commodatedifferential contractions and eXpansionsiand also materially increasethe heat con- In the `specific illustrative form `which has the iiuidcarrying members allows free expanbeen described the spiral tube form ofone of sion and contraction `of that member with the longitudinalchanges of dimension of the other member which is here shown as tubular;`While the expansion joints 2|] in the latter'zmember accommodate thatmember to `the lateral or i circumferential contractionsand expansionsof f the first mentioned or spiralmember.

`It is of course to `be understood that the drawing, and description are`to be considered as merely illustrative of the invention in one of itspossible practical forms, and; that various'` `changes in design,structure and arrangement may be made Without departing from the spiritand scope ofthe claim.

I claim:

In heat vexchange apparatus,l the combination of a fluid carrying memberhaving `a heatconductive, fluidconning Wall ofgeneral tubularformation,A said Wall including' a :plurality of ly, from the innersurface of those portions of the wall which liebetween the indentations,into the interior of the tubular `member to form inter,-nalhollowheatconductive ns, said indentations being externally Open tothe surrounding atmosphere` at their outer edges and forming fluidconfining portions of the wall which also provide `for circumferentialcontraction and expansion; means connected with an end of the tubularlmember for feeding a fluid exclusively through the interior of saidmember, the interiors of the open indentations being `isolated from thefluid feed; and another fluid carrying member composed of a helicallycoiled tube with` longitudinally spaced turns closely surrounding theindented tubular Wall, :physically and heat-` conductively integratedwith the `Wall betWeenI the circumferentially spaced indentations, andbridging their outer openings.

GILBERT E ciuirIc-Y.`

invention or of the appended

